The challenge of antimicrobial glazed ceramic surfaces

The resistance that microorganisms develop to antibiotics is a worldwide challenge. The antimicrobial agents as disinfectants for surface treatments are widespreadly used to prevent the proliferation of microorganisms, but their use should be repeated over time to ensure a complete microbe-free surface. Surfaces with permanent antimicrobial properties suppose a recent demand in materials science for functional polymeric coatings, metals, treated wood or ceramic glazed tiles. Whereas polymeric coating has been extensively studied, the antimicrobial functionality on ceramic glazed surfaces is not completely achieved. This work reviews glazed ceramic tiles developments in antimicrobial and virucidal surfaces. The main antimicrobial physical or chemical mechanisms have been described as the base to develop active glazed surfaces. The main tests required to evaluate the antimicrobial response in glazed ceramic tiles are also summarized. The high temperature required in the ceramic processing is the key point to achieve a micro/nanostructure that potentiates the antimicrobial and virucidal response of the glazed surfaces. A discussion on recent developments as well as the main routes and challenges to obtain permanent surfaces with antimicrobial and virucidal response is provided.     

Effect of porosity on the elastic properties of porcelainized stoneware tiles by a multi-layered model

Porcelainized stoneware represents a leading product in the world market of ceramic tiles, thanks to its relevant bending strength (with respect to other classes of tiles) and extremely low water absorption: these properties derive from its really low content of residual porosity. Nevertheless, an accurate investigation of the cross section of a porcelainized stoneware tile reveals a non-uniform distribution of the residual pores through the thickness, which results in a spatial gradient of properties. Porcelainized stoneware, therefore, may be looked at as a functionally graded material. In the present research, commercial porcelainized stonewares were analysed in order to define the effect of the residual porosity and its spatial distribution on the mechanical properties of tiles. Polished cross sections of porcelainized stoneware tiles were investigated by optical and scanning electron microscopy in order to define the content and distribution of residual pores as a function of distance from the working surface. For each porcelainized stoneware, the local elastic properties of the ceramic matrix were measured by a depth-sensing Vickers micro-indentation technique, then the so-obtained microstructural images and elastic properties were used to model the stoneware tile mechanical properties. In particular, the cross section of each tile was described as a multi-layered system, each layer of which was considered as a composite material formed by a ceramic matrix and residual pores. The elastic properties of each layer were predicted by applying analytical equations derived from the theory of composite materials and, as a new approach, by performing microstructure-based finite element simulations. In order to validate the proposed multi-layered model and identify the most reliable predictive technique, the numerical results were compared with experimental data obtained by a resonance-based method.     

无釉砖和有釉砖耐磨性标准的统一化探析

耐磨性是陶瓷砖的一项关键性能指标,目前GB/T 4100—2015《陶瓷砖》规定无釉砖和有釉砖采用不同的试验方法。利用耐深度磨损试验机、陶瓷砖釉面耐磨试验机和Taber试验机对无釉砖和有釉砖进行耐磨性的测定,研究同一种试验方法是否能同时对两种陶瓷砖作精确的评判。结果表明,无釉砖耐磨深度法和Taber耐磨试验法可通过磨损体积的大小对无釉砖进行耐磨性的测定,但两者都不适合用于有釉砖耐磨性的测定。有釉砖表面耐磨法用磨耗质量大小取代目视评价可得到更客观和精准的结果,可同时用于无釉砖和有釉砖耐磨性的测定。     

新型节能原料-透辉石在釉面砖中的节能机理

依据透辉石矿物结构特征,分析讨论了该矿物原料独有的热学性能和工艺特性,阐述了其在釉面砖生产中的节能机理。     

抗菌功能陶瓷釉面砖的研究

通过在釉中引入银系无机抗菌剂,研制了低温一次快烧的具有抗菌功能的陶瓷釉面砖。采用陶瓷试验系统（ｃｅｒａｍｉｃ ｍｅｃｈａｎｉｃａｌ ｔｅｓｔ ｓｙｓｔｅｍ,ＭＴＳ）用ＳＥＭ,ＥＰＭＡ等测定了材料的理化性能及微观结构。结果表明,该材料具有良好的抗菌性、耐久性及坯釉结合性,其他技术性能均达到国标。     

Chemical hardening of glazed porcelain tiles

Glazed ceramic tiles are used for wall and floor covering thanks to their high resistance to chemicals attacks, although big efforts should be done to increase their surfaces resistance to mechanical stresses. This study investigates the applicability of a well-known glass hardening process to glazed ceramic tiles following a rational design based on Design of Experiments technique. A Mixture Design has been carried out to formulate new frits compositions to enhance the ion-exchange process, starting from a commercial product. Vickers Hardness and SEM-EDS techniques have been employed to evaluate the frits and elaborate the model. Results suggest that frits for ceramic tiles are positively affected by ion-exchange process only if an appropriate combination of ions in the starting composition is present, establishing a new category of frit formulations suitable for that purpose. The results have been confirmed employing the optimized frit for the glazing of porcelain stoneware.     

PVD hard coatings on ceramic tiles for aesthetic applications: surface characterisation and corrosion properties

The development of innovative ceramic tiles looks for materials with improved mechanical and tribological properties as well as a higher corrosion resistance (high relative humidity, daily watering, household chemical cleaners). In addition, a greater durability leads to lower environmental impact. Along with their improved functionality and recyclability, ceramic tiles should also provide aesthetic properties. Ceramic tiles can be treated to modify the physico-chemical properties of the surface by metal coatings or metallic compounds, also providing an attractive metallic sheen appearance. In the present paper, titanium nitride (TiN) and zirconium nitride (ZrN) coatings were deposited on glazed porcelain stoneware by an industrial PVD multicathode arc deposition system under a reactive nitrogen atmosphere. After the process, the tiles showed a gold-like colour, a smooth surface and a coating thickness between 0.7 and 1.6 μm. The coating composition, scratch resistance and corrosion behaviour have been evaluated. It can be concluded that both coatings are suitable for use in domestic environments due to their stability and resistance to aggressive conditions. Few references have been found regarding these coatings on ceramic tiles for domestic and industrial applications, but it has been proved that they bring added value to traditional ceramics, giving new functional properties of ceramics both decorative and highly corrosion and mechanical resistance.     

Evaluation of durability and cleanability performances of protective treatments for lapped ceramic tiles - Part 2

The aim of this work is to evaluate the cleanability performances of lapped porcelain stoneware surfaces with and without protective treatments. The knowledge of the material cleanability is an important selection parameter in buying tiles. However, an objective basis for testing and assessing this property still is lacking. In this study, standardized and laboratory tests to evaluate the cleanability performance of lapped porcelain stoneware products have been carried out and compared. Cleanability tests were performed by applying two different soiling suspensions, optimized for tile surfaces and reproducing chemical and mechanical actions simulating the working conditions and traditional cleaning operations. Surface characteristics (microstructure, topography, roughness) were analyzed before and after cleanability tests. The results showed a good correlation between different behavior in terms of cleanability and the microscopic and topographic characteristics of lapped tile. Respect to international standardized tests specific for ceramic tiles, such as stains resistance test, the laboratory procedures to evaluate the surface cleanability are able to better show cleanability improvements of lapped tiles with protective treatments.     

Use of Gabbro in Production of Facing Ceramic Tiles

The advantages of using gabbro rock, which is rich in calcium and magnesium oxides, in the production of ceramic facing tiles, instead of raw materials containing calcium and magnesium carbonates are discussed. It is shown that by adding ceramic tile scrap and increasing the slip viscosity, it is possible to improve the product quality and change over to one-stage firing of glazed tiles.     

Hydro deformation in ceramic tiles at the pre-firing stage

The production of ceramic tiles with larger sizes and reduced thickness has increased the challenge of producing high-quality ceramic tiles in short single-firing cycles. For porcelain tiles, the pressing step is of upmost importance for the microstructure of the green bodies. The particle size distribution, mineral composition of the pastes and porosity before firing define the water flow during the decoration process. Hydro deformation is the curvature of unfired ceramic tiles caused by water absorption during the decoration step before firing. In this work, the hydro deformation is studied in function of tile thickness, compaction, and clay composition according to a 2^K factorial design. Two compositions of porcelain tiles (glazed and polished) were pressed at two thicknesses (3–6 mm) and pressing pressures (35.5–49.8 MPa) forming ceramic tiles with 55 × 110 mm² of surface area. Chemical (XRF), mineralogical (XRD), thermogravimetric (TG), specific surface area (BET), granulometric, bulk density, and porosity analyses were performed for the green tiles of both compositions. To simulate the hydro deformation during the decoration step, the curvature (mm) of the tiles was studied within a 0–180 min interval. The water absorption rate through the surface (g.m⁻²·s⁻¹) of the tiles in an interval of 0–180 s was studied as a function of thickness, pressure and porcelain tile composition. As a result, the thickness of the tiles can change the curvatures from concave to convex. Pressing conditions and composition of the tiles can change the water absorption rates. Porcelain tiles with higher content of clay minerals develop convex curvatures. For tiles with lower content of clay minerals, concave curvatures were developed.     

陶瓷内墙釉面砖吸湿膨胀的研究

阐述了陶瓷内墙釉面砖吸湿膨胀的产生原因及降低吸湿膨胀的一般方法。针对某种产品吸湿膨胀率较大的问题,利用生产废料调整了生产配方。新试制产品在吸湿膨胀率方面符合国家标准要求,在其它主要性能方面也明显得到提高。     

复合型陶瓷薄板的制备及其力学性能

作为一种轻薄、低能耗的功能化产品,陶瓷薄板因强度低而应用受限,如何对其进行低成本增强成为工业领域研究热点。本文以构筑“纤维布-黏结剂-陶瓷薄板”多层复合结构作为切入点,将多种工业级纤维布、黏结剂和陶瓷薄板进行二次后加工复合,制备了兼具低成本和优异力学性能的复合型陶瓷薄板,探究了其断裂面微观形貌及断裂机理。经研究表明,“碳纤维布-环氧树脂-陶瓷薄板”复合型陶瓷薄板具有最佳界面结合强度及力学性能,其抗弯强度和承载冲击能量分别为85.26 MPa和1.45 J,与陶瓷薄板坯体相比,性能提升幅度分别高达22.98%和141.67%。“纤维布-黏结剂-陶瓷薄板”多层复合结构能够有效提升陶瓷薄板综合力学性能,陶瓷薄板内部存在微裂纹拓展、纤维偏转等多种良性强韧化机制。     

On-site pXRF analysis of glaze composition and colouring agents of “Iznik” tiles at Edirne mosques (15th and 16th-centuries)

The production of the tiles in Ottoman Empire had begun as a continued workshop of Seldjuk ceramic art, and after this initial phase, its own technology was introduced into Ottoman art by local craftsmen. Iznik tiles are among the most appreciated pottery masterpieces, and wall decoration in tiles is a significant asset of Unesco World Heritage Edirne mosques. Rare glaze composition studies have been made, which justify the need for more comprehensive studies. We present here the first on-site elemental analyses performed with portable XRF instrument in four of the most representative mosques in Edirne (?ah Melek Pa?a (1429), Muradiye (1435–1436), Üç ?erefeli (1410–1447) and Selimiye (1569–1575)). A handheld 785?nm Raman spectrometer was used as a complementary technique to identify some pigments. About forty tiles have been analysed in this research. Additionally, two tiles from Ye?ilce Mosque (1442, Edirne) have been analysed at the Selimiye Foundation Museum. The weight percent of the elements measured with pXRF are normalized by Si amount in order to eliminate the variation due to the positioning shifts. Different glazing technologies are evidenced (Master of Tabriz Sn-free glazed tiles, Hünkar Mahfili Sn-poor glazed tiles, and Sn-(Bi) rich ones). At least three different cobalt ores have been used (with characteristic Cu, Ni, Mn and Bi content) in blue decors. Use of a chromium-based ore is demonstrated for some Selimiye Hünkar Mahfili tiles. The link between ?ah Melek Pa?a and polychrome (mihrab) Muradiye tiles and Seldjuk production is established. On the contrary, the technology of Üç ?erefeli and blue-and-white Muradiye tiles is unique and appears a precursor of 16th-century Iznik production. Bismuth, Sn/Pb, Co/Mn, and Co/Ni ratio appears very useful to compare the different glazes and to identify mining sources of cobalt.     

Self‐Cleaning and Antibacteric Ceramic Tile Surface

The aim of this investigation was the surface functionalization of industrial ceramic tiles by sol‐gel technique to improve at the same time the cleanability and the antibacterial activity of surfaces. This objective was pursued through the design and preparation of nanostructured titania‐silver coating that was deposited on glazed, unglazed, and polished tiles by air‐brushing. The obtained results showed that the applied coatings are transparent, show a good adhesion, and a remarkable antibacterial activity under the tested conditions. The surface photocatalicity was optimized with the higher thermal treatments (200°C) even if photodegradation process is clearly affected by the sample surface roughness.     

Steel particles–porcelain stoneware composite tiles: An advanced experimental–computational approach

Innovative porcelain stoneware tiles with a surface layer containing 2.4 wt% of stainless-steel particles were produced by the Double Charge Technology. Considering this layer as a composite material, the effects of the metal particles on the mechanical behaviour of the ceramic matrix were extensively investigated in terms of Young's modulus, fracture toughness and flexural strength. With this aim, composite materials were prepared by using the same silicate-based ceramic matrix with increasing weight percentages of the same stainless-steel powder. The composites were accurately characterised. In particular, due to the high sintering temperature, possible changes at the interface between metal particles and ceramic matrix were thoroughly analysed by means of SEM and EDS microanalysis. To clarify the role of the observed chromium-rich interphase on the mechanical behaviour of the steel particles–stoneware composites, analytical equations were used and simulations were performed by using the Object Oriented Finite (OOF) element method.     

传统陶瓷耐磨性能评价方法

本文介绍了现有的传统陶瓷产品耐磨性能测试方法与标准,分析了这些测试方法用于测试传统陶瓷耐磨性能的可行性和不足之处,提出可以统一有釉砖与无釉砖耐磨性能测试方法与标准。     

提高陶瓷砖釉面硬度的途径

有釉砖具有良好的装饰效果,但是釉面硬度较低,容易出现划痕。本文概述了有釉砖的釉面硬度、耐磨性的检测方法。并通过分析影响有釉砖釉面硬度的因素．提出了通过调整配方组成、引入微晶玻璃、改进工艺制度、进行表面处理等途径可提高有釉砖的釉面硬度。     

Relationship between certain ceramic roofing tile characteristics and biodeterioration

This paper examines the relationship of certain red ceramic roofing tile properties to roofing tile biodeterioration. The following properties were studied: apparent porosity, roughness, and the presence or absence of two types of coatings.The effect of apparent porosity was studied by varying the peak firing temperature of a standard industrial red ceramic roofing tile composition and by preparing several clay mixtures, of different chemical and mineralogical composition, that were fired at various peak temperatures. The effect of roofing tile roughness was determined by either polishing or sanding fired standard red roofing tiles. A waterproof ceramic glaze coating and a photocatalytic coating were formulated to analyse the effect of the presence of different types of coatings. Roofing tile bioreceptivity was evaluated with a method developed in a previous study using the cyanobacteria Oscillatoria sp, which enabled roofing tile resistance to microbial colonization to be determined.As expected, bioreceptivity rose as apparent porosity (measured as water absorption) increased, enabling possible water retention, which favours biological growth. Similarly, greater roughness encouraged micro-organism adhesion and raised bioreceptivity. It was found that, after prolonged exposure periods (several months) under very favourable conditions for biological colonization, roofing tiles coated with the waterproof ceramic glaze were colonized. However, glazed standard red roofing tiles covered with a TiO₂ photocatalytic coating exhibited practically no biological growth under the test conditions used, even after long exposure times, owing to the chemical-physical effect of the TiO₂-based coating.     

Evaluation of durability and cleanability performances of protective treatments for lapped ceramic tiles—Part 1

The aim of this work was to evaluate the durability, in real pedestrian traffic condition, of lapped porcelain stonewares with surface protective treatments able to fill up pores opened by the lapping process. In recent years, the durability of ceramic surfaces has become a key factor during the design process. The knowledge of the material durability is important to define the behavior of tiles in use. Standard procedures for indirectly assessing durability are already available (ie, abrasion tests, staining resistance, chemical resistance), however, a standard method of aging in real condition is still lacking. In this study, a durability test was performed in real pedestrian traffic condition by fixing tiles on floors to evaluate the surface characteristics after 6 and 12 months. The surface characteristics were analyzed before and after the durability tests and in terms of microstructural observations and determination of surface porosity. In particular a durability index has been estimated as ratio of pores filled by dirtiness respect to the original surface porosity (before aging). Results of durability index showed good correlation between aging duration and kind of treatments (industrially applied and/or manually applied).     

Laser-assisted glass-based sealing of polished porcelain stoneware tile surface to increase stain resistance

This study aims to develop a new approach for the permanent sealing of surface pores on polished porcelain stoneware tiles, using ceramic frits for the filling pores, followed by laser-sealing to ensure the fixation of the applied material. The laser-sealing parameters compatible with the ceramic substrate were focus height (z) of 105 mm, scan speed (v) of 2640 mm.min⁻¹, and power values of 750, 800, and 850 W. In order to define the working parameters, three ceramic frits with 30, 50, and 70 wt.% solid contents were tested by sealing at the mentioned powers. High stain resistant polished stoneware tiles were obtained using frit 1 and frit 3 with 50 and 70 wt.% solid contents, respectively, and the proposed procedure. High ease of cleaning is obtained related to the current treatment, demonstrating its suitability for improving the stain resistance for meeting the ISO 13006:2012 requirements.